/*
 * Distributed as part of mchange-commons-java 0.2.6.5
 *
 * Copyright (C) 2014 Machinery For Change, Inc.
 *
 * Author: Steve Waldman <swaldman@mchange.com>
 *
 * This library is free software; you can redistribute it and/or modify
 * it under the terms of EITHER:
 *
 *     1) The GNU Lesser General Public License (LGPL), version 2.1, as 
 *        published by the Free Software Foundation
 *
 * OR
 *
 *     2) The Eclipse Public License (EPL), version 1.0
 *
 * You may choose which license to accept if you wish to redistribute
 * or modify this work. You may offer derivatives of this work
 * under the license you have chosen, or you may provide the same
 * choice of license which you have been offered here.
 *
 * This software is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.
 *
 * You should have received copies of both LGPL v2.1 and EPL v1.0
 * along with this software; see the files LICENSE-EPL and LICENSE-LGPL.
 * If not, the text of these licenses are currently available at
 *
 * LGPL v2.1: http://www.gnu.org/licenses/old-licenses/lgpl-2.1.html
 *  EPL v1.0: http://www.eclipse.org/org/documents/epl-v10.php 
 * 
 */

package com.ddm.server.common.utils;

import java.io.IOException;
import java.io.StringReader;
import java.io.StringWriter;

public final class ByteUtils {
    public final static short UNSIGNED_MAX_VALUE = (Integer.MAX_VALUE * 2) + 1;

    public static short toUnsigned(byte b) {
        return (short) (b < 0 ? (UNSIGNED_MAX_VALUE + 1) + b : b);
    }

    public static String toHexAscii(byte b) {
        StringWriter sw = new StringWriter(2);
        addHexAscii(b, sw);
        return sw.toString();
    }

    public static String toHexAscii(byte[] bytes) {
        int len = bytes.length;
        StringWriter sw = new StringWriter(len * 2);
        for (int i = 0; i < len; ++i) {
            addHexAscii(bytes[i], sw);
        }
        return sw.toString();
    }

    public static byte[] fromHexAscii(String s) throws NumberFormatException {
        try {
            int len = s.length();
            if ((len % 2) != 0) {
                throw new NumberFormatException("Hex ascii must be exactly two digits per byte.");
            }

            int out_len = len / 2;
            byte[] out = new byte[out_len];
            int i = 0;
            StringReader sr = new StringReader(s);
            while (i < out_len) {
                int val = (16 * fromHexDigit(sr.read())) + fromHexDigit(sr.read());
                out[i++] = (byte) val;
            }
            return out;
        } catch (IOException e) {
            throw new InternalError("IOException reading from StringReader?!?!");
        }
    }

    static void addHexAscii(byte b, StringWriter sw) {
        short ub = toUnsigned(b);
        int h1 = ub / 16;
        int h2 = ub % 16;
        sw.write(toHexDigit(h1));
        sw.write(toHexDigit(h2));
    }

    private static int fromHexDigit(int c) throws NumberFormatException {
        if (c >= 0x30 && c < 0x3A) {
            return c - 0x30;
        } else if (c >= 0x41 && c < 0x47) {
            return c - 0x37;
        } else if (c >= 0x61 && c < 0x67) {
            return c - 0x57;
        } else {
            throw new NumberFormatException('\'' + c + "' is not a valid hexadecimal digit.");
        }
    }

    /* note: we do no arg. checking, because */
    /* we only ever call this from addHexAscii() */
    /* above, and we are sure the args are okay */
    private static char toHexDigit(int h) {
        char out;
        if (h <= 9) {
            out = (char) (h + 0x30);
        } else {
            out = (char) (h + 0x37);
        }
        // System.err.println(h + ": " + out);
        return out;
    }

    private ByteUtils() {
    }
}
